Amplifier circuits



April 2l, 1925. 4 F. E. FIELD AMPLIFIER CIRCUITS File-d Dez. l. 1922 Patented Apr. 21,1925.

UNITED STATES PATENT OFFICE.

FRANK E. IEIID, OF SOMERVILLE, NEW JERSEY, ASSIGNOR T0 ATES'IIERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION 0F NEW YORK.

AMPLIFIER CIRCUITS.

Application led December 1, 1922. Serial No. 604,154. j

To aZZ whoa/z,v 'it may conocia:

Be it known that I, FRANK E. Fmm, a

lcitizen of the United States, residing at Somerville, in the county of Somerset, State of New Jersey', have invented certain new and useful Improvements in Amplifier Circuits, of which the following is a full, clear, concise, and exact description.

This invention relates to amplifier circuits having means for adjustment in their input circuit, and has for an object, to avoid singing vdue to electrostatic coupling'between the output circuit and the input circuit.

.A further objectl of the invention is to avoid disturbances due to the manual operation of a switch. in an amplifier circuit.,

In the form of the invention disclosed herein, a switch makes adjustable connection to taps on the secondary winding of the input transformer for adjusting the gain of the amplifier.v Since the metallic mass of the switch is relatively large, its capacity to conductors in the output'circuit is much .larger than that of the lead wires in the input circuit. It has been found that if the switch-is kconnected to the grounded cathode andthe xed terminal of the secondary winding connected to the grid by a short lead wire, the tendency of the circuit to sing is very greatly reduced. Disturbances due to accidental contact of the operators hand with the metallic portions of the switch are also minimized.

The invention will be more fully understoodV from the following detailed-'descriptionand claims taken with the accompanying drawing which shows schematically a vacuum tube amplifier circuit embodying the invention.

. Referring tol the drawings by reference numerals, the input transformer 5 im resses signalson the vacuum tube 7, and t e amplified signals are impressed by a transformer 9 ona second amplifier stage, comprisingvacuum tubes 11 and 12 in the socalled .pushpull relation. Connection is made to any suitable work circuit'by an output transformer 14.

The secondary winding of input transformer 5 is provided with taps 16 and con .nection is made to these taps by a switch ,17 for adjusting the amplification. `Switch 17 is connected to the cathode heating circuit which is grounded at 18. This .insures thatthe switch 17 remains at the potential of the grounded portions of the output circuit and reduces very greatly the electrostatic feed-back of energy from the output circuit to the input eircut. For the same reason the lead wire connecting the ungrounded terminal 20 of the secondary winding to the grid is made as short as possible.

While only a single form of the invention has been shown, it4 is' to be understood that the invention may assume other forms within the scope'of the appended claims.

The invention claimed is:

1. In combination, a source of incoming signal Waves, a space discharge tubetranslating device supplied with said waves, said l device having a cathode, anode and control electrode, an impedance connected effectively across said source, one end of said impedance being conductively connected to said controlelectrode by a short conductor, a

plurality of taps on said impedance for ad-` j justing the potential of said waves supplied to said device, and a switch conductively connected to said cathode and to ground, said switch having a contact adjustably engaging said taps.

2. In combination, a source of incoming signal waves, a space discharge tube translating device supplied with said waves, said device having a cathode, anode and control electrode, a transformer connected between said source and 'said device, the primary of said transformer being connected t0 said source, one end of the secondary of. said transformer being conductively connected to said control electrode by a short conductor,l

a plurality of taps on said secondary of said transformer for adjusting the potential of said waves supplied to said device, and a switch conductively connected to said cathode and to ground, said switch having av FRANK E. FIELD. 

